1. Field of the Invention
This invention relates to an electronic volume varying apparatus which includes a controlling section for outputting a controlling signal to control an electronic volume in response to pulses from an operating section and also to an input pulse detecting method for processing or ignoring a chattering portion which appears at a trailing end of an input pulse from an operating section to detect the input pulse as well as a pulse switch apparatus to which the input pulse detecting method can be applied suitably.
2. Description of the Prior Art
Electronic volume varying apparatus which include a controlling section for outputting a controlling signal to control an electronic volume in response to pulses from an operating section are already known. An exemplary one of such conventional electronic volume varying apparatus is shown in FIG. 8.
Referring to FIG. 8, the electronic volume varying apparatus shown includes a rotary pulse generator 1 serving as an operating section. The rotary pulse generator 1 has such construction as shown in FIG. 9 and outputs an output pulse or pulses in accordance with a direction of rotation thereof. In particular, the rotary pulse generator 1 outputs an up pulse or pulses P.sub.U when it rotates in one direction but outputs a down pulse or pulses P.sub.D when it rotates in the opposite direction.
The electronic volume varying apparatus further includes a controlling section 2. The controlling section 2 includes a pulse inputting device 21 for outputting either an up pulse confirmation signal P.sub.US representative of confirmation of an up pulse P.sub.U from the rotary pulse generator 1 or a down pulse confirmation signal P.sub.DS representative of confirmation of a down pulse P.sub.D from the rotary pulse generator 1. A pulse counting device 22 outputs either up pulse count data D.sub.U representative of a count value of up pulse confirmation signals P.sub.US received from the pulse inputting device 21 or down pulse count data D.sub.D representative of a count value of down pulse confirmation signals P.sub.DS received from the pulse inputting device 21. A memory device 23 stores therein up pulse count data D.sub.U or down pulse count data DD received from the pulse counting device 22, and an arithmetic unit 24 calculates control data D.sub.C for controlling an electronic volume 3 in accordance with count data D.sub.1 or D.sub.D recalled from the memory device 23 and outputting the control data D.sub.C to the memory device 23 and sends the control data D.sub.C to the memory device 23 so that they are stored into the memory device 23. A data outputting device 25 outputs a controlling signal S.sub.C in accordance with control data D.sub.C recalled from the memory device 23 to the electronic volume 3.
The electronic volume 3 attenuates a sound volume signal S.sub.A supplied from an external circuit not shown in accordance with the controlling signal S.sub.C received from the data outputting device 25 of the controlling section 2 and outputs an attenuation signal S.sub.AA obtained by the attenuation.
An amplifier 4 amplifies the attenuation signal S.sub.AA received from the electronic volume 3 and supplies it to a loudspeaker 5.
In operation, when an up pulse P.sub.U is outputted from the rotary pulse generator 1, the pulse inputting device 21 outputs an up pulse confirmation signal P.sub.US. The pulse counting device 22 counts the up pulse confirmation signal P.sub.US and outputs up pulse count data D.sub.U. Consequently, the memory device 23 stores therein the up pulse count data D.sub.U.
The arithmetic unit 24 calculates control data D.sub.C in accordance with the up pulse count data D.sub.U of the memory device 23 and stores them back into the memory device 23. The data outputting device 25 recalls the control data D.sub.C, produces a controlling signal S.sub.C in accordance with the control data D.sub.C and outputs the controlling signal S.sub.C therefrom.
The electronic volume 3 attenuates a sound volume signal S.sub.A supplied thereto from the external circuit in accordance with the controlling signal S.sub.C and outputs an attenuation signal S.sub.AA obtained by the attenuation. The attenuation signal S.sub.AA is amplified by the amplifier 4 and sent to the loudspeaker 5. Consequently, sound the volume of which is adjusted in accordance with the attenuation signal S.sub.AA is generated from the loudspeaker 5.
It is to be noted that, when a down pulse P.sub.D is outputted from the rotary pulse generator 1, the controlling section 2, electronic volume 3 and amplifier 4 operate in a similar manner so that sound the volume of which is, in this instance, decreased in accordance with the attenuation signal S.sub.AA is generated from the loudspeaker 5.
The conventional electronic volume varying apparatus is constructed in such a manner as described above, and since the rotary pulse generator 1 does not have a position indication representative of a turning position of a manually operable knob or dial, a set condition of the electronic volume 3 cannot be discriminated.
Further, though not shown, the conventional electronic volume varying apparatus is constructed such that the electronic volume 3 is controlled in response to an up pulse PU or a down pulse PD generated from the rotary pulse generator 1 independently of a muting operation.
Accordingly, when the electronic volume varying apparatus is applied, for example, to a cassette deck which is constructed such that it enters a muting mode when it is put into a fast feeding (FF) mode or a rewinding (REW) mode, if the rotary pulse generator 1 is rotated in the up direction in a muting mode of the cassette deck, then the sound volume increases suddenly immediately after cancellation of the muting mode. Consequently, a listener may be surprised by the great sound volume.
The rotary pulse generator described above has such a construction as shown, for example, in FIG. 9. Referring to FIG. 9, the rotary pulse generator shown includes a fastening plate 101 having an elliptic hole 101a formed at a central portion thereof. An elliptic portion of a shaft 107 is fitted in the elliptic hole 101a of the fastening plate 101 as shown in FIG. 10. The fastening plate 101 further has a pair of fitting fingers 101b formed thereon across the elliptic hole 101a such that they extend in an axial direction of the elliptic hole 101a.
The rotary pulse generator further includes a spacer 102 having a hole 102a formed at a central portion thereof. The fitting pieces 101b of the fastening plate 101 extend through the hole 102a of the spacer 102.
The rotary pulse generator further includes a movable contact plate 103 mounted for integral rotation with the fastening plate 101 and the shaft 107. The movable contact plate 103 includes a movable plate 103a having a hub 103a.sub.1 which has a bore 103a.sub.11 formed therein. The fitting fingers 101b of the fastening plate 101 and the shaft 107 are fitted in the bore 103a.sub.11 of the hub 103a.sub.1 of the movable contact plate 103 such that, when the shaft 107 is manually rotated, it rotates the fastening plate 101 and the movable contact plate 103 together therewith. The movable contact late 103 further has a contact plate 103b having conducting portions 103b.sub.1 and non-conducting portions 103b.sub.2 provided alternately at a suitably spaced relationship, for example, in an equidistantly spaced relationship, on a common circle around the hub 103a.sub.1 of the movable plate 103a.
The rotary pulse generator further includes a ball 104 made of a conducting material and mounted such that it rolls on the conducting portions 103b.sub.1 and non-conducting portions 103b.sub.2 of the contact plate 103b.
The rotary pulse generator further includes an insulating casing 105 having a ball box 5a provided thereon for holding the ball 104 for rolling movement thereon. A common terminal 106A is mounted on the insulating casing 105 such that it is noramlly held in contact with the contact plate 103b, and first and second terminals 106B and 106C are mounted on the insulating casing 105 such that the first terminal 106B is contacted with the ball 104 when the contact plate 103b is rotated in a first direction (up direction) but the second terminal 106C is contacted with the ball 104 when the contact plate 103b are rotated in a second direction (down direction) opposite to the first direction.
When the components 101 to 107 are assembled in position, the ball 104 contacts with a contacting portion 103b.sub.1 of the movable contact plate 103 and also with the first terminal 106B so that it is held from movement in the leftward direction as shown, for example, in FIGS. 10 and 11a.
In this condition, if the shaft 107 is rotated in the counterclockwise direction, that is, first or up direction, then the fastening plate 101 and the movable contact plate 103 are rotated in the same direction by the shaft 107. During such counterclockwise rotation, the ball 104 is alternately contacted with the conducting portions 103b.sub.1 and the non-conducting portions 103b.sub.2 so that such up pulses P.sub.u as shown by a curve (a) in FIG. 12 are generated between the common terminal 106A and the first terminal 106B.
Then, if the rotation of the shaft 107 is stopped at a point of time t.sub.1, then generation of such up pulses P.sub.u is stopped in a condition wherein an up pulse P.sub.u rises.
Then, if the shaft 107 is rotated further in the counterclockwise direction from its stopped position from a point of time t.sub.2 after lapse of a predetermined interval of time, then the pulse P.sub.u then falls as indicated by a solid line of the curve (a) in FIG. 12 and further up pulses P.sub.U are generated as indicated by a broken line of the curve (a) in FIG. 12 between the common terminal 106A and the first terminal 106B.
On the contrary, if the shaft 107 is rotated in the opposite, clockwise direction, that is, second or down direction, from the point of time t.sub.2, then the fastening plate 101 and the movable contact plate 103 are rotated by the shaft 107. Thereupon, the ball 104 is spaced away from the first terminal 106B and now brought into contact with the second terminal 106C as seen from FIG. 11b. Thus, the last up pulse P.sup.U falls as indicated by the solid line portion of the curve (a) in FIG. 12 when the ball 104 is spaced away from the first terminal 106B, and after then, down pulses P.sub.D are generated as seen from another curve (b) in FIG. 12 after the ball 104 is contacted with the second terminal 106C.
Since the conventional rotary pulse generator is constructed in such a manner as described above, when the shaft 107 is stopped at a normal position at which the ball 104 contacts with a conducting portion 103b.sub.1 of the movable contact plate 103, a pulse P.sup.U or P.sub.D is generated as described above.
However, due to the structure of the rotary pulse generator, when the shaft 107 is rotated in the counterclockwise direction in FIG. 10 and then stopped, it sometimes stops at a position at which the ball 104 is displaced any conducting portion 103b.sub.1 but contacts with a non-conducting portion 103b.sub.2 of the contact plate 103 as shown in FIG. 11c.
If the shaft 107 is rotated in the clockwise direction in this condition, then the ball 104 will be contacted, when the movable contact plate 103 is rotated, with a conducting portion 103b.sub.1 before it is spaced away from the first terminal 106B. Consequently, down pulses P.sub.D will be generated as seen from a curve (b) in FIG. 13 after an up pulse P.sub.U is generated as seen from another curve (a) in FIG. 13.
Although detailed description is omitted, also when the shaft 107 is rotated in the counterclockwise direction, a similar situation may occur.
Accordingly, although the shaft 107 is rotated in a predetermined direction, a pulse of a direction opposite to the predetermined direction is generated inadvertently.
In order to eliminate the disadvantage, it is necessary to provide a click mechanism for establishing a predetermined positional relationship between the movable contact plate 103 and the ball 104 to stop the shaft 107 at a predetermined position. However, even if a click mechanism is provided, it sometimes occurs that the shaft 107 is not stopped at any of the predetermined positions. Consequently, the disadvantage described above still remains not solved.
Further, when such a rotary pulse generator is employed as an operating section for such an electronic volume varying apparatus as described above, an input pulse from the rotary pulse generator to the electronic volume varying apparatus often has a chattering portion at a rear or trailing end thereof. Such chattering portion will obstruct accurate detection of the input pulse. Conventionally, an input pulse is detected in accordance with such an input pulse detecting method as described below.
In particular, referring to FIG. 14, there is shown an input pulse P having a chattering portion P.sub.T which appears at a trailing end thereof. An input signal including such input pulse P is sampled in a sampling period S.sub.1, which is used to detect presence or absence of an input pulse P and, when an input pulse P is present, process or ignore a chattering portion P.sub.T of the input pulse P.
Thus, the input signal is successively sampled for each sampling period S.sub.1, and when the sampled value first presents a predetermined input pulse value continuously for a plurality of periods such as at points of time t.sub.3 to t.sub.5 and then presents the value 0, it is detected as one input pulse P.
With the conventional input pulse detecting method, if the sampling period S.sub.1 is made so long that the chattering portion P.sub.T shown in FIG. 14 may not be identified as a portion of an input pulse P, then in case the width of the input pulse P is shorter than the sampling period S.sub.1, the input pulse P cannot be detected accurately.
On the contrary, if the sampling period S.sub.1 is made so short that an input pulse P of a minimum width may be detected, then the chattering portion P.sub.T is sometimes detected as an input pulse P. Accordingly, it is not possible to process the chattering portion P.sub.T to detect an input pulse accurately with the single sampling period S.sub.1.